Field of Invention
The present invention relates to a technical field of fully hydraulic drilling machine, and more particularly to a mechanism for twisting off a drill rod which is capable of disassembling and assembling the drill rod in the course of drilling operations.
Description of Related Arts
A mechanism for twisting off a drill rod is a key assembly of a fully hydraulic drilling machine, which is mainly adapted for screwing on and off the drill rod and is capable of clamping the drill rod in a hole to avoid slippage of the drill rod and drilling tool. The disassembly torque of the drill rod of the heavy-load drilling machine is able to reach over one hundred thousand Newton meter. Therefore, whether the performance of the mechanism for twisting off the drill rod is good will directly affect the drilling and disassembly efficiency of the drilling machine. Currently, there are two types of the mechanism for twisting off the drill rod, which is adopted by the fully hydraulic drilling machine, namely, a mechanism for twisting off a single drill rod and a mechanism for twisting off double drill rods. The mechanism for twisting off the drill rod comprises a base, an oil cylinder and a clamping jaw. The mechanism for twisting off double drill rods is adapted for automatically assembling and disassembling the drill rods, thereby the operation is simple and the labor intensity is decreased.
The conventional mechanism for twisting off the drill rod, as shown in FIGS. 7 and 8, comprises a positioning clamping oil cylinder 4 and a clamping assembly 3, wherein one end of an overturn oil cylinder 2 is hinged with a base 9, the other end thereof is hinged with a rear end of an overturn clamping body through a pin 1. The operational principle of the above mentioned conventional mechanism for screwing in the drill rod is as follows. While screwing in a drill rod, a piston rod of the clamping oil cylinder 4 within a fixed clamping body firstly stretches out to drive the clamping assembly 3 to tightly clamp a female wire end of a first drill rod (which has been drilled-in during the course of construction, and then a piston rod of the clamping oil cylinder within the overturn clamping body stretches out to drive the clamping assembly to tightly clamp a male wire end of a second drill rod (which is newly drilled in), and then a power head male wire is rotated into a female wire end of the second drill rod through a power head rotational torque, once finished, the clamping oil cylinder within the overturn clamping body is loosened, and simultaneously, the power head moves forwardly and rotates to screw the male wire end of the second drill rod into the female wire end of the first drill rod of the fixed clamping body. The operational principle of the above mentioned conventional mechanism for screwing off the drill rod is as follows. While screwing off one drill rod, the power head firstly moves backwardly to drive the male wire end of the first drill rod to the overturn clamping body, and the clamping oil cylinder of the overturn clamping body tightly clamps the male wire end of the first drill rod, the clamping oil cylinder of the fixed clamping body tightly clamps the female wire end of the second drill rod connected with the first drill rod which needs to be screwed off, and then the overturn oil cylinder stretches out, the overturn clamping body turns over upwardly and takes a central hole of the fixed clamping body as a center, the front and rear positioning rings installed on the overturn clamping body matches an intermediate hole, so as to loosen the first drill rod which is tightly clamped by the overturn clamping body, and then the clamping oil cylinder of the overturn clamping body loosens the drill rod, the power head rotates to drive the screw thread of the first drill rod to loosen. After loosening two drill rod ends, the clamping oil cylinder of the overturn clamping body tightly clamps the male wire end of the first drill rod again, the connect threads of both the female wire end of the first drill rod and the power head are screwed out by the power head rotational torque. The above operations are remotely controlled by an electronic control system for automatically disassembling the drill rod. During the above operations, the mechanism for twisting off the drill rod frequently works, needs a very high requirement for positioning while clamping the drill rod. However, in practice, due to various tubing length and resistance, in spite that the clamping assembly comprises multiple friction pieces, the drill rod which is clamped by the overturn clamping body is not concentric with the drill rod which is clamped by the fixed clamping body, so that the screw threads are severely worn while assembling and disassembling.
In prior arts, JP No. 2003-074286A discloses an equipment for clamping a drill rod. To resolve the center deviation of the drill rod while the left and right clamping bodies clamping the drill rod 5, firstly, the clamping oil cylinder 2 with large diameter drives the clamping jaw 24 to move forwardly to stop at a desired central position, and then the clamping oil cylinder 3 with small diameter drives another clamping jaw 34 to move forwardly to clamp the drill pipe 5. The above mentioned technical solution has shortcomings as follows. One clamping force of the clamping oil cylinder is big, and another clamping force thereof is small. While clamping, it is required that the clamping force of the clamping oil cylinder with large diameter should be equal to that of the clamping oil cylinder with small diameter, so that the control of the oil circuit is complicated. During working process, the left and right clamping slips are stressed unevenly, so that it is easy to eccentric again. Due to the clamping force of the clamping oil cylinder with small diameter, the nominal clamping force of the clamping equipment is limited.
In prior arts, the left and right clamping oil cylinders are symmetrically installed to the bracket relatively to the central axis of the drill pipe, as shown in FIG. 8, so that it is very easy to offset from the central line while clamping.
Based on the shortcomings of the above prior arts, after being improved, a breakout mechanism, with simple structure, not easy to eccentric, with short centering time and oil control simplification, is provided by the applicants of the present invention.